Aliens vs. Predator

This achievement should be a lot easier now judging by the fact that few people do Deathmatch anymore, which means you are likely to be in a match against 2-3 other people, which is obviously better than the 12 person match that I got it on. If you really need help though, just find 2-3 other people who need it too, make each other preferred players, filter search to 8 players, and begin searching for a deatch match at the same time. Obviously you cant all be in the same group, in case you didn't know :)
Men, Welcome to the War

Edit: To clear up any confusion, deathmatches require a minimum of 3 players to start. So if you're setting up a boosting session, make sure you have at least 3 people unless you don't mind a few random players.

Edit 2: Since presumably the online is dead at this point, The Noir Plague offered this comment: "For those looking to do the AvP 2010 Multiplayer achievements 10 years later, I've set up a discord to hopefully bring enough people together: https://discord.gg/77dWa3a" I recommend joining it, assuming it is still active if you are reading this years from now

You don't even need to win a deathmatch for this achvievement to unlock.

I got this last night playing with 2 other players. One of them left in the lobby which left one on one.
I just hid for the entire match in a dark corner (cloaked as the predator) and went away for 10 minutes.

The game ended a draw but somehow this achvievement unlocked.